(a) Field of the Invention
This invention relates to novel compounds classified in the field of organic chemistry as 3,7-bis[4-(disubstituted amino)phenyl]- or (indol-3-yl)-3,7-bis(diphenylamino)pyromellitides and 3,5-bis[4-(disubstituted amino)phenyl]- or (indol-3-yl)-3,5-bis(diphenylamino)pyromellitides and mixtures thereof useful as color precursors, particularly in the art of carbonless duplicating, for example, pressure-sensitive and thermal marking systems; to processes for preparing the pyromellitides; and to pressure-sensitive and thermal marking systems containing the pyromellitides.
(b) Description of the Prior Art
Several classes of organic compounds of widely diverse structural types are known to be useful as colorless precursors for carbonless duplicating systems. Among the more important classes, there may be named phenothiazines, for example, benzoyl leuco methylene blue; phthalides, for example, crystal violet lactone; fluorans, for example, 2'-anilino-6'-diethylaminofluoran and 2'-dibenzylamino-6'-diethylaminofluoran; and various other types of colorless precursors currently employed in commercially accepted carbonless copy systems. Typical of the many such systems taught in the prior art are those described in U.S. Pat. Nos. 2,712,507, 2,800,457 and 3,041,289 which issued July 5, 1955, July 23, 1957 and June 26, 1962, respectively. Many of the color formers in the prior art suffer one or more disadvantages such as low tinctorial strength, poor light stability, low resistance to sublimation, low susceptibility to copiability of the color-developed form in standard copying machines, for example, a Xerox.RTM. copier, and low solubility of common organic solvents, the last-mentioned disadvantage thus requiring the use of specialized and expensive solvents in order to obtain microencapsulated solutions of sufficient concentration for use in pressure-sensitive copying machines.
The following items to date appear to constitute the most relevant prior art with regard to the instant invention.
U.S. Pat. No. 3,268,537, issued Aug. 23, 1966, discloses and claims a mixture of two isomeric pyromellitides, individually of the formulas ##STR1## in which the Xs are selected from the group consisting of 9-julolidinyl, 4-aminophenyl and mono- and disubstituted 4-aminophenyl moieties. The compounds are disclosed to be colorless when dissolved in solvents normally used in carbonless duplicating systems and develop dark-colored images upon contact with suitable color-developing substances, for example, an acidic clay. The pyromellitides of this patent are prepared through the intermediates 2,5-[bis(4-dialkylaminophenyl)carbonyl]-1,4-benzenedicarboxylic acid and 2,4-[bis(4-dialkylaminophenyl)carbonyl]-1,5-benzenedicarboxylic acid, respectively.
U.S. Pat. No. 3,491,117, issued Jan. 20, 1970, discloses and claims a chromogenic pyromellitide selected from the group consisting of: ##STR2## and mixtures thereof, where R.sub.1, R.sub.2, R.sub.3 and R.sub.4 consist of 1,2-dialkylindol-3-yl and p-dialkylaminophenyl groups wherein alkyl has less than five carbon atoms, such that at least two indolyl radicals are present in a cis relationship in compounds having a cis configuration and in a trans relationship in compounds having a trans configuration. The chromogenic compounds are disclosed as being useful in pressure-sensitive recording systems. The pyromellitides disclosed in this patent are prepared through 2,4-[bis(4-dialkylaminophenyl-, or indolyl)carbonyl]-1,5-benzenedicarboxylic acid and 2,5-[bis(4-dialkylaminophenyl-, or indolyl)carbonyl]-1,4-benzenedicarboxylic acid, respectively.
Fawcett, Cassidy and Lin in the Journal of Organic Chemistry 42 (17), 2929-2930 (1977) describe the preparation and physical characteristics of 3,3,5,5-tetraphenylpyromellitide and 3,3,7,7-tetraphenylpyromellitide from the interaction of 4,6-dibenzoylisophthalic acid or 2,5-dibenzoylterephthalic acid and benzene in the presence of aluminum chloride. No indication of utility for the compounds is given in the article.
Belgian Pat. No. 862,217, published June 22, 1978, which corresponds essentially to U.S. Pat. Nos. 4,168,378 and 4,182,714 which issued Sept. 18, 1979 and Jan. 8, 1980, respectively, in the names of Paul Joseph Schmidt and William Mo-Wei Hung, the inventors in the instant application, discloses a series of phthalides useful as color formers in pressure-sensitive carbonless duplicating systems, thermal marking systems and hectographic or spirit-reproducing copying systems and having the formula ##STR3## wherein Q is di-lower-alkylamino, nitro, halo or COX, where X is hydroxyl, benzyloxy, alkoxy having from 1 to 18 carbon atoms or OM where M is an alkali metal cation, an ammonium cation or a mono-, di- or tri-alkylammonium cation having from 1 to 18 carbon atoms; n is 0; or 1 when Q is di-lower-alkylamino, nitro or COX; or from 1 to 4 when Q is halo; Y.sub.1, Y.sub.2, Y.sub.3 and Y.sub.4 are the same or different and are hydrogen, halo, hydroxyl, lower-alkoxy, alkyl having from 1 to 9 carbon atoms, phenyl-lower-alkyl, COOR.sub.4 or NR.sub.5 R.sub.6, where R.sub.4 and R.sub.5 are hydrogen or lower-alkyl and R.sub.6 is hydrogen, lower-alkyl, cycloalkyl having from 5 to 7 carbon atoms or lower alkanoyl; Z is chosen from the group consisting of ##STR4## in which R is hydrogen or non-tertiary alkyl having from 1 to 4 carbon atoms; R.sub.1 is hydrogen or non-tertiary alkyl having from 1 to 18 carbon atoms; R.sub.2 is hydrogen, phenyl or non-tertiary alkyl having from 1 to 4 carbon atoms; R.sub.3 is hydrogen, non-tertiary alkyl having from 1 to 4 carbon atoms or non-tertiary alkoxy having from 1 to 4 carbon atoms; R.sub.7 is hydrogen, halo, lower-alkyl lower-alkoxy or di-lower-alkylamino; R.sub.8 is lower-alkyl; and R.sub.9 is lower-alkyl, benzyl, phenyl or phenyl substituted with a lower-alkyl or lower-alkoxy group.